Process for preparing polysiloxane-polycarbonate block cocondensates

ABSTRACT

The present invention relates to a process for preparing polysiloxane-polycarbonate block cocondensates proceeding from specific polycarbonates and hydroxyaryl-terminated polysiloxanes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application (under 35 U.S.C. §371)of PCT/EP2014/071297, filed Oct. 6, 2014, which claims benefit ofEuropean Application No. 13187749.0, filed Oct. 8, 2013, both of whichare incorporated herein by reference in their entirety.

The present invention relates to a process for preparingpolysiloxane-polycarbonate block cocondensates proceeding from specificpolycarbonates and hydroxyaryl-terminated polysiloxanes.

The invention further relates to the polysiloxane-polycarbonate blockcocondensates which have been obtained by the process according to theinvention, and to the use of these cocondensates in injection mouldingand extrusion applications.

BACKGROUND OF THE INVENTION

It is known that polysiloxane-polycarbonate block cocondensates havegood properties with regard to low-temperature impact strength orlow-temperature notched impact strength, chemical resistance and outdoorweathering resistance, and to aging properties and flame retardancy. Interms of these properties, they are in some cases superior to theconventional polycarbonates (homopolycarbonate based on bisphenol A).

The industrial preparation of these cocondensates proceeds from themonomers, usually via the interfacial process with phosgene. Also knownis the preparation of these siloxane cocondensates via the melttransesterification process using diphenyl carbonate. However, theseprocesses have the disadvantage that the industrial plants usedtherefore are used for preparation of standard polycarbonate andtherefore have a high plant size. The preparation of specific blockcocondensates in these plants is often economically unlivable because ofthe smaller volume of these products. Moreover, the feedstocks requiredfor preparation of the cocondensates, for example polydimethylsiloxanes,impair the plant, since they can lead to soiling of the plant or of thesolvent circuits. In addition, toxic feedstocks such as phosgene arerequired for the preparation, or these processes entail a high energydemand.

The preparation of polysiloxane-polycarbonate block copolymers via theinterfacial process is known from the literature and is described, forexample, in U.S. Pat. No. 3,189,662, U.S. Pat. No. 3,419,634, DE-B 3 34782 and EP 122 535.

The preparation of polysiloxatie carbonate block copolymers by the melttransesterification process from bisphenol, diaryl carbonate and silanolend-terminated polysiloxanes in the presence of a catalyst is describedin U.S. Pat. No. 5,227,449. The siloxane compounds used arepolydiphenyl- or polydimethylsiloxane telomers with silanol end groups.It is known, however, that such dimethylsiloxanes having silanol endgroups, in contrast to diphenylsiloxane with silanol end groups, have anincreasing tendency to self-condensation with decreasing chain length inan acidic or basic medium, such that incorporation into the copolymer asit forms is made more difficult as a result. Cyclic siloxanes formed inthis process remain in the polymer and have an exceptionally disruptiveeffect in applications in the electrical/electronics sector.

U.S. Pat. No. 5,504,177 describes the preparation of a blockcopolysiloxane carbonate via melt transesterification from acarbonate-terminated silicone with bisphenol and diaryl carbonate.Because of the great incompatibility of the siloxanes with bisphenol anddiaryl carbonate, homogeneous incorporation of the siloxanes into thepolycarbonate matrix can be achieved only with very great difficulty, ifat all, via the melt transesterification process. Furthermore, thepreparation of the block cocondensates proceeding from the monomers isvery demanding.

EP 770636 describes a melt transesterification process for preparationof block copolysiloxane carbonates proceeding from bisphenol A anddiaryl carbonate using specific catalysts. A drawback of this process islikewise the demanding synthesis of the copolymer proceeding from themonomers.

U.S. Pat. No. 5,344,908 describes the preparation of asilicone-polycarbonate block copolymer via a two-stage process in whichan OH-terminated BPA oligocarbonate prepared via a melttransesterification process is reacted with a chlorine-terminatedpolyorganosiloxane in the presence of an organic solvent and of an acidscavenger. Such two-stage processes are likewise very demanding and canbe performed only with difficulty in industrial scale plants.

Disadvantages of all these processes are the use of organic solvents inat least one step of the synthesis of the silicone-polycarbonate blockcopolymers, the use of phosgene as a feedstock and/or the inadequatequality of the cocondensate. More particularly, the synthesis of thecocondensates proceeding from the monomers is very demanding, both inthe interfacial process and particularly in the melt transesterificationprocess. For example, in the case of the melt process, a small relativeunderpressure and low temperatures have to be employed, in order toprevent vaporization and hence removal of the monomers. Only in laterreaction stages in which oligomers with higher molar mass have formedcan lower pressures and higher temperatures be employed. This means thatthe reaction has to be conducted over several stages and that thereaction times are accordingly long.

In order to avoid the above-described disadvantages, there are alsoknown processes which proceed from commercial polycarbonates. This isdescribed, for example, in U.S. Pat. No. 5,414,054 and U.S. Pat. No.5,821,321. Here, a conventional polycarbonate is reacted with a specificpolydimethylsiloxane in a reactive extrusion process. A disadvantage ofthese processes is the use of highly active transesterificationcatalysts which enable the preparation of the cocondensates within shortresidence times in an extruder. These transesterification catalystsremain in the product and can be inactivated only inadequately, if atall. Therefore, injection mouldings made from the cocondensates thusprepared have inadequate aging characteristics, more particularlyinadequate thermal aging characteristics. Moreover, it is necessary touse specific and hence expensive siloxane blocks.

DE 19710081 describes a process for preparing the cocondensatesmentioned in a melt transesterification process proceeding from anoligocarbonate and a specific hydroxyarylsiloxane. The preparation ofthe oligocarbonate is also described in this application. However, theindustrial scale preparation of oligocarbonates for preparation ofrelatively small-volume specific cocondensates is very costly andinconvenient. These oligocarbonates have relatively low molecularweights and relatively high OH end group concentrations. Frequently,these oligocarbonates, because of their short chain length, havephenolic OH concentrations above 1000 ppm. Such products are notnormally commercially available and would therefore have to be producedspecifically for the preparation of the cocondensates. However, it isuneconomic to operate industrial scale plants with the production ofsmall-volume precursors. Moreover, such precursors, because of theimpurities present in these products, for example residual solvents,residual catalysts, unreacted monomers etc., are much more reactive thanhigh molecular weight commercial products based on polycarbonate. Forthese reasons, corresponding precursors or aromatic oligocarbonatessuitable for the preparation of such block cocondensates arecommercially unavailable. Moreover, the process described in DE 19710081does not allow preparation of block cocondensate within short reactiontimes. Both the preparation of the oligocarbonate and the preparation ofthe block cocondensate are affected over several stages with residencetimes totaling well over one hour. Furthermore, the resulting materialis unsuitable for the preparation of cocondensates, since the highconcentration of OH end groups and other impurities, for examplecatalyst residue constituents, lead to a poor colour in the end product.

None of the abovementioned applications describes a process whichproceeds from conventional polycarbonates commercially available inprinciple and affords polysiloxane-polycarbonate block cocondensates inhigh quality.

High quality in this context means that the cocondensates can beprocessed in injection moulding or by extrusion processes and have arelative solution viscosity of preferably at least 1.26, more preferablyat least 1.27, especially preferably at least 1.28, determined indichloromethane at a concentration of 5 g/l at 25° C. using a Ubbelohdeviscosimeter. Furthermore, the corresponding products must have a highmelt stability. In addition, the products should not have anydiscoloration such as browning or yellowing.

Commercially available polycarbonates have only low reactivity and, incontrast to the above-described oligocarbonates or polycarbonateprecursors, are very melt-stable. In other words, they can be compoundedunder the customary processing conditions or can be processed ininjection moulding or in extrusion without restriction and without anychange in the properties. The person skilled in the art thus assumesthat these polycarbonates, which may also contain stabilizers orquenchers, are unsuitable for preparation of copolymers because of theirhigh stability.

Proceeding from the prior art outlined, the problem addressed wastherefore that of developing an inexpensive process for the preparationof the cocondensates mentioned, which does not require toxic feedstockssuch as phosgene. A further objective was to avoid preparation of suchcocondensates from the monomers, i.e. proceeding from the low molecularweight bisphenols and organic carbonates such as diphenyl carbonate,since this is very demanding and requires a costly standardpolycarbonate synthesis or copolycarbonate synthesis in a correspondingindustrial scale plant. Instead, the process according to the inventionis to enable the preparation of the cocondensates proceeding frompolycarbonates commercially available in principle. Such processes are,for example, transesterification processes described in principle in theliterature—for example in U.S. Pat. No. 5,414,054. However, there is noknown process which affords the cocondensates in comparable quality tothat in the interfacial process. A further problem addressed wastherefore that of developing a process which affordspolysiloxane-polycarbonate block cocondenates in high quality, such thatthe materials are suitable for injection moulding and extrusionapplications. Furthermore, the process is to afford the block copolymerwithin a short reaction time. Typically, the formation of polycarbonatesby the melt transesterification process proceeds in several stages withhigh residence times (for example greater than one hour until therespective target viscosity has been attained). In contrast, the blockcopolymer is to be prepared in the appropriate target viscosity withinshort reaction times.

Moreover, inexpensively preparable siloxane components are to be usedfor preparation of block cocondensates. Frequently, several reactionstages, some under platinum or ruthenium catalysis, are needed forpreparation of the siloxane blocks. This considerably increases thecosts of preparation of these siloxane blocks and leads to discolorationin the polysiloxane-polycarbonate block cocondensate product. Therefore,in the process according to the invention, the intention is to usesiloxane blocks which do not have to be prepared via processes whichentail ruthenium and/or platinum catalysis and which do not containimpurities that could be dentrimental to the properties of the resultingcocondensate product. Such unwanted impurities could be for examplestrong bases in general, salts of hydroxy- or halogen ions amines andheavy metals.

BRIEF SUMMARY OF THE INVENTION

It has been possible, surprisingly, to develop a process in whichparticular polycarbonates containing particular rearrangement structureswith specific OH end group concentrations and specifichydroxyaryl-terminated polysiloxanes can be converted under particularconditions to high-quality polysiloxane-polycarbonate blockcocondensates. It has additionally been found that, surprisingly, thecorresponding polycarbonates need to have particular rearrangementstructures to be suitable for the process according to the invention.The process according to the invention further has the advantage ofrequiring no solvents and fewer or no subsequent purification stepscompared to the processes of the prior art.

The present invention therefore provides a process for preparingpolysiloxane-polycarbonate block cocondensates, in which at least onehydroxyaryl-terminated siloxane of the formula (1) (siloxane component)

-   -   in which    -   R¹ is H, Cl, Br or C₁ to C₄-alkyl, preferably H or methyl, and        especially preferably H,    -   R² and R³ are the same or different and each independently from        one another selected from aryl, C₁ to C₁₀-alkyl and C₁ to        C₁₀-alkylaryl, preferably R² and R³ are methyl,    -   X is a single bond, —CO—, —O—, C₁- to C₆-alkylene, C₂ to        C₅-alkylidene, C₅ to C₁₂-cycloalkylidene or C₆ to C₁₂-arylene        which may optionally be fused to further aromatic rings        containing heteroatoms, X preferably being a single bond, C₁ to        C₅-alkylene, C₂ to C₅-alkylidene, C₅ to C₁₂-cycloalkylidene, —O—        or —CO—, X more preferably being a single bond, isopropylidene,        C₅- to C₁₂-cycloalkylidene or oxygen, and most preferably        isopropylidene,    -   n is a number from 1 to 500, preferably from 10 to 400,        especially preferably from 10 to 100, most preferably from 20 to        60,    -   m is a number from 1 to 10, preferably from 1 to 6, especially        preferably from 2 to 5, and    -   p is 0 or 1, preferably 0,    -   and the value of n times m is preferably between 12 and 400,        more preferably between 15 and 200;        is reacted with at least one polycarbonate in the melt at        temperatures of 280° C. to 400° C., preferably of 300° C. to        390° C., more preferably of 320° C. to 380° C. and most        preferably of 330° C. to 370° C., and pressures of 0.001 mbar to        50 mbar, preferably 0.005 mbar to 40 mbar, especially preferably        0.02 to 30 mbar, and most preferably 0.03 to 5 mbar, preferably        in the presence of a catalyst.

DETAILED DESCRIPTION OF THE INVENTION

Preferably, the polycarbonate has a weight-average molecular weight of16 000 to 28 000 g/mol, preferably of 17 000 to 27 000 g/mol, andespecially preferably of 18 000 to 26 500 g/mol, determined by means ofgel permeation chromatography and BPA (bisphenol A) standard, andphenolic OH groups in an amount of 250 ppm to 1000 ppm, preferably 300to 900 ppm and especially preferably of 350 to 800 ppm.

In a preferred embodiment, the polycarbonate has a relative solutionviscosity (eta rel) of 1.16 to 1.30, preferably 1.17 to 1.28, and morepreferably 1.18 to 1.27, determined in dichloromethane at aconcentration of 5 g/l at 25° C. using a Ubbelohde viscosimeter.

Through the process according to the invention, the corresponding blockcocondensates are obtainable within short reaction times. “Shortreaction time” in this context means the reaction time which is requiredto condensate the low molecular weight polycarbonate (from a moltenstate) to the block cocondensate having the target viscosity and havingincorporated the siloxane component. The reaction time is preferablyless than one hour, especially preferably less than 50 minutes and mostpreferably less than 40 minutes. Especially preferably, the blockcopolymer is prepared in a process having fewer than 3 stages,especially preferably having fewer than two stages, not counting themelting and mixing of reactants and any catalysts as a stage. Individualstages mean, for example, the conduction of the reaction at particulartemperatures and pressures (for example one stage at 200° C. and 100mbar, a second stage at 50 mbar and 250° C., and a third stage at 10mbar and 300° C., each with particular residence times).

The polycarbonates for use in accordance with the invention contain atleast one, preferably more than one, of the following structures (I) to(IV):

-   -   in which    -   the phenyl rings are unsubstituted or independently mono- or        disubstituted by C₁ to C₈-alkyl and/or halogen, preferably C₁ to        C₄-alkyl, more preferably methyl,

X is a single bond, C₁ to C₆-alkylene, C₂ to C₅-alkylidene or C₅ toC₆-cycloalkylidene, preferably a single bond or C₁ to C₄-alkylene, andespecially preferably isopropylidene,

-   -   the linkages indicated by        in the structural units (I) to (IV) are each part of a        carboxylate group;    -   and wherein the amount of the structural units (I) to (IV)        totals 60 to 1500, preferably 70 to 1200 ppm, and most        preferably 80 to 850 ppm (determined after hydrolysis, based on        the polycarbonate).

Preference is additionally given to polycarbonates which bear phenol asend groups (phenyl-terminated polycarbonate).

If a polycarbonate contains none or only small amounts of theserearrangement structures, the reaction with the abovementioned siloxanecomponents is possible only to a very minor extent, if at all.Polycarbonates which do not contain any of the structures (I) to (IV)(also called rearrangement structures hereinafter) are thus unsuitablefor the process according to the invention. This was very surprising,since it was unknown to date that rearrangement structures have anyinfluence on the reactivity of the polycarbonate. Furthermore, it wasnot known before that such polycarbonates can be used for thepreparation of siloxane-containing copolycarbonates.

The preparation of polycarbonates containing the structural elements (I)to (IV) on the industrial scale is known in principle and is described,for example, in DE 102008019503.

Polycarbonates in the context of the present invention are bothhomopolycarbonates and copolycarbonates.

Preferred modes of preparation of the polycarbonates for use inaccordance with the invention, including the polyestercarbonates,proceed by the known melt transesterification process.

Some, preferably up to 80 mol %, more preferably from 20 mol % up to 50mol %, of the carbonate groups in the polycarbonates suitable inaccordance with the invention may be replaced by aromatic dicarboxylicester groups. Such polycarbonates, which contain both acid radicals ofthe carbonic acid and acid radicals of aromatic dicarboxylic acidsincorporated into the molecule chain, are, to be exact, aromaticpolyestercarbonates. For the sake of simplicity, they are to be coveredin the present application by the umbrella term of thermoplasticaromatic polycarbonates.

Polycarbonates are prepared in a known manner from diphenols, carbonicacid derivatives, optionally chain terminators and optionally branchingagents, with replacement of a portion of the carbonic acid derivativesby aromatic dicarboxylic acids or derivatives of the dicarboxylic acidsfor preparation of the polyestercarbonates, specifically by aromaticdicarboxylic ester structural units according to the carbonatestructural units to be replaced in the aromatic polycarbonates.

By way of example for the preparation of polycarbonates, reference ismade here to Schnell, “Chemistry and Physics of Polycarbonates”, PolymerReviews, Volume 9, Interscience Publishers, New York, London, Sydney1964.

Diphenols suitable for the process according to the invention forpreparation of polycarbonates have been described many times in theprior art.

Suitable diphenols are, for example, hydroquinone, resorcinol,dihydroxydiphenyl, bis(hydroxyl-phenyl)alkanes, bis(hydroxyphenyl)sulphides, bis(hydroxyphenyl) ethers, bis(hydroxyphenyl)ketones,bis(hydroxyphenyl) sulphones, bis(hydroxyphenyl) sulphoxides,α,α′-bis(hydroxyl-phenyl)diisopropylbenzenes, and the alkylated,ring-alkylated and ring-halogenated compounds thereof.

Preferred diphenols are 4,4′-dihydroxydiphenyl,2,2-bis(4-hydroxyphenyl)1-phenylpropane,1,1-bis(4-hydroxyphenyl)phenylethane, 2,2-bis(4-hydroxyphenyl)propane,2,4-bis(4-hydroxyphenyl)2-methylbutane,1,3-bis[2-(4-hydroxyphenyl)2-propyl]benzene (bisphenol M),2,2-bis(3-methyl-4-hydroxyphenyl)propane,bis(3,5-dimethyl-4-hydroxyphenyl)methane,2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane,bis(3,5-dimethyl-4-hydroxyphenyl) sulphone,2,4-bis(3,5-dimethyl-4-hydroxyphenyl)2-methylbutane and1,3-bis[2-(3,5-dimethyl-4-hydroxyphenyl)2-propyl]benzene,

Particularly preferred diphenols are 4,4′-dihydroxydiphenyl,1,1-bis(4-hydroxyphenyl)phenylethane and2,2-bis(4-hydroxyphenyl)propane,2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane. These and further suitableother dihydroxyaryl compounds are described, for example, in DE-A 3 832396, FR-A 1 561 518, in H. Schnell, Chemistry and Physics ofPolycarbonates, interscience Publishers, New York 1964, p. 28 ff.; p.102 ff. and in D. G. Legrand, J. T. Bendler, Handbook of PolycarbonateScience and Technology, Marcel Dekker New York 2000, p. 72 ff.

In the case of the homopolycarbonates, only one diphenol is used; in thecase of the copolycarbonates, a plurality of diphenols are used; it willbe appreciated that the diphenols used, and also all the other chemicalsand assistants added to the synthesis, may be contaminated with theimpurities originating from their own synthesis, handling and storage,although it is desirable to work with raw materials of maximumcleanliness.

The polycarbonates can be modified in a conscious and controlled mannerby the use of small amounts of chain terminators and branching agents.Suitable chain terminators and branching agents are known from theliterature, Some are described, for example, in DE-A 38 33 953.Preferably used chain terminators are phenol or alkylphenols, inparticular phenol, p-tert-butyl-phenol, isooctylphenol, cumylphenol, thechlorocarbonic acid esters thereof or acid chlorides of monocarboxylicacids or mixtures of these chain terminators. Preferred chainterminators are phenol, cumylphenol, isooctylphenol,para-tert-butylphenol, and in particular phenol.

Examples of compounds suitable as branching agents are aromatic oraliphatic compounds having at least three, preferably three or four,hydroxyl groups. Particularly suitable examples having three or morethan three phenolic hydroxyl groups are phloroglucinol,4,6-dimethyl-2,4,6-tri(4-hydroxy-phenyl)hept-2-ene,4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptane,1,3,5-tri(4-hydroxyphenyl)-benzene, 1,1,1-tri(4-hydroxyphenyl)ethane,tri(4-hydroxyphenyl)phenylmethane,2,2-bis(4,4-bis(4-hydroxyphenyl)cyclohexyl]propane,2,4-bis(4-hydroxyphenylisopropyl)phenol, tetra(4-hydroxy-phenyl)methane.

Examples of other trifunctional compounds suitable as branching agentsare 2,4-dihydroxybenzoic acid, trimesic acid, cyanuric chloride and3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.

Particularly preferred branching agents are3,3-bis(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole and1,1,1-tri(4-hydroxyphenyl)ethane.

The diaryl carbonates suitable for the reaction with the dihydroxyarylcompounds in the melt transesterification are those of the generalformula (2)

-   -   in which    -   R, R′ and R″ are the same or different and are each        independently hydrogen, linear or branched C₁-C₃₄-alkyl,        C₇-C₃₄-alkylaryl or C₆-C₃₄-aryl,        -   R may additionally also be —COO—R′″ where R′″ is hydrogen,            linear or branched C₁-C₃₄-alkyl, C₇-C₃₄-alkylaryl or            C₆-C₃₄-aryl.

Preferred diaryl carbonates are, for example, diphenyl carbonate,methylphenyl phenyl carbonates and di(methylphenyl)carbonates,4-ethylphenyl phenyl carbonate, di(4-ethylphenyl)carbonate,4-n-propylphenyl phenyl carbonate, di(4-n-propylphenyl)carbonate,4-isopropylphenyl phenyl carbonate, di(4-isopropylphenyl)carbonate,4-n-butylphenyl phenyl carbonate, di(4-n-butylphenyl)carbonate,4-isobutylphenyl phenyl carbonate, di(4-isobutylphenyl)carbonate,4-tert-butylphenyl phenyl carbonate, di(4-tert-butylphenyl)carbonate,4-n-pentylphenyl phenyl carbonate, di(4-n-pentylphenyl)carbonate,4-n-hexylphenyl phenyl carbonate, di(4-n-hexylphenyl)carbonate,4-isooctylphenyl phenyl carbonate, di(4-isooctylphenyl)carbonate,4-n-nonylphenyl phenyl carbonate, di(4-n-nonylphenyl)carbonate,4-cyclohexylphenyl phenyl carbonate, di(4-cyclohexylphenyl)carbonate,4-(1-methyl-1-phenylethyl)phenyl phenyl carbonate,di[4-(1-methyl-1-phenylethyl)phenyl]carbonate, biphenyl-4-yl phenylcarbonate, di(biphenyl-4-yl)carbonate, 4-(1-naphthyl)phenyl phenylcarbonate, 4-(2-naphthyl)phenyl phenyl carbonate,di[4-(1-naphthyl)phenyl]carbonate, di[4-(2-naphthyl)phenyl]carbonate,4-phenoxyphenyl phenyl carbonate, di(4-phenoxyphenyl)carbonate,3-pentadecylphenyl phenyl carbonate, di(3-pentadecylphenyl)carbonate,4-tritylphenyl phenyl carbonate, di(4-tritylphenyl)carbonate, (methylsalicylate)phenyl carbonate, di(methyl salicylate)carbonate, (ethylsalicylate)phenyl carbonate, di(ethyl salicylate)carbonate, (n-propylsalicylate)phenyl carbonate, di(n-propyl salicylate)carbonate,(isopropyl salicylate)phenyl carbonate, di(isopropylsalicylate)carbonate, (n-butyl salicylate)phenyl carbonate, di(n-butylsalicylate)carbonate, (isobutyl salicylate)phenyl carbonate, di(isobutylsalicylate)carbonate, (tert-butyl salicylate)phenyl carbonate,di(tert-butyl salicylate)carbonate, di(phenyl salicylate)carbonate anddi(benzyl salicylate)carbonate.

Particularly preferred diaryl compounds are diphenyl carbonate,4-tert-butylphenyl phenyl carbonate, di(4-tert-butylphenyl)carbonate,biphenyl-4-yl-phenyl carbonate, di(biphenyl-4-yl)carbonate,4-(1-methyl-1-phenylethyl)phenyl phenyl carbonate,di[4-(1-methyl-1-phenylethyl)phenyl]carbonate and di(methylsalicylate)carbonate.

Very particular preference is given to diphenyl carbonate.

It is possible to use either one diaryl carbonate or else various diarylcarbonates.

The diaryl carbonates can also be used with residual contents of themonohydroxyaryl compounds from which they have been prepared. Theresidual contents of the monohydroxyaryl compounds may be up to 20% byweight, preferably up to 10% by weight, more preferably up to 5% byweight and most preferably up to 2% by weight.

Based on the dihydroxyaryl compound(s), generally 1.02 to 1.30 mol ofthe diaryl carbonate(s), preferably 1.04 to 1.25 mol, more preferably1.045 to 1.22 mol and most preferably 1.05 to 1.20 mol per mole ofdihydroxyaryl compound are used. It is also possible to use mixtures ofthe abovementioned diaryl carbonates, in which case the above-statedmolar figures per mole of dihydroxyaryl compound relate to the totalamount of the mixture of the diaryl carbonates.

The catalysts used in the melt transesterification process forpreparation of polycarbonates may be the basic catalysts known in theliterature, for example alkali metal and alkaline earth metal hydroxidesand oxides and/or onium salts, for example ammonium or phosphoniumsalts. Preference is given to using onium salts in the synthesis, morepreferably phosphonium salts. Such phosphonium salts are, for example,those of the general formula (3)

-   -   in which    -   R⁴⁻⁷ are identical or different, optionally substituted        C₁-C₁₀-alkyl, C₆-C₁₄-aryl, C₇-C₁₅-arylalkyl or C₅-C₆-cycloalkyl        radicals, preferably methyl or C₆-C₁₄-aryl, more preferably        methyl or phenyl, and    -   X⁻ is an anion selected from the group of hydroxide, sulphate,        hydrogensulphate, hydrogencarbonate, carbonate, halide,        preferably chloride, and alkoxide or aroxide of the formula —OR⁸        where R⁸ is an optionally substituted C₆-C₁₄-aryl,        C₇-C₁₅-arylalkyl, C₅-C₆-cycloalkyl or C₁-C₂₀-alkyl radical,        preferably phenyl.

Particularly preferred catalysts are tetraphenylphosphonium chloride,tetraphenylphosphonium hydroxide and tetraphenylphosphonium phenoxide,very particular preference being given to tetraphenylphosphoniumphenoxide.

The catalysts are used preferably in amounts of 10⁻⁸ to 10⁻³ mol, morepreferably in amounts of 10⁻⁷ to 10⁻⁴ mol, based on one mole ofdihydroxyaryl compound.

It is optionally also possible to use cocatalysts in order to increasethe rate of polycondensation.

These may, for example, be alkaline salts of alkali metals and alkalineearth metals, such as hydroxides, optionally substitutedC₁-C₁₀-alkoxides and C₆-C₁₄-aroxides of lithium, sodium and potassium,preferably hydroxides, optionally substituted C₁-C₁₀-alkoxides orC₆-C₁₄-aroxides of sodium. Preference is given to sodium hydroxide,sodium phenoxide or the disodium salt of2,2-bis(4-hydroxyphenyl)propane.

If alkali metal or alkaline earth metal ions are supplied in the form oftheir salts, the amounts of alkali metal or alkaline earth metal ions,determined, for example, by atomic absorption spectroscopy, is 1 to 500ppb, preferably 5 to 300 ppb and most preferably 5 to 200 ppb, based onpolycarbonate to be formed. In preferred embodiments of the processaccording to the invention, however, no alkali metal salts are used.

The performance of the polycarbonate synthesis may be continuous orbatchwise.

“C₁-C₄-alkyl” in the context of the invention is, for example, methyl,ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl;“C₁-C₆-alkyl” is additionally, for example, n-pentyl, 1-methylbutyl,2-methylbutyl, 3-methylbutyl, neopentyl, 1-ethylpropyl, cyclohexyl,cyclopentyl, n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl,1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl,1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl,2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl,2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl,1-ethyl-1-methylpropyl or 1-ethyl-2-methylpropyl; “C₁-C₁₀-alkyl” isadditionally, for example, n-heptyl and n-octyl, pinacyl, adamantyl, theisomeric menthyls, n-nonyl, n-decyl; C₁-C₃₄-alkyl is additionally forexample, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl orn-octadecyl. The same applies to the corresponding alkyl radical, forexample, in aralkyl or alkylaryl, alkylphenyl or alkylcarbonyl radicals.Alkylene radicals in the corresponding hydroxyalkyl or aralkyl oralkylaryl radicals are, for example, alkylene radicals corresponding tothe above alkyl radicals.

“Aryl” is a carbocyclic aromatic radical having 6 to 34 skeletal carbonatoms. The same applies to the aromatic moiety of an arylalkyl radical,also called aralkyl radical, and to aryl constituents of more complexgroups, for example arylcarbonyl radicals.

Examples of “C₆-C₃₄-aryl” are phenyl, o-, p-, m-tolyl, naphthyl,phenanthrenyl, anthracenyl or fluorenyl.

“Arylalkyl” or “aralkyl” is in each case independently a straight-chain,cyclic, branched or unbranched alkyl radical as defined above, which maybe singly, multiply or fully substituted by aryl radicals as definedabove.

The above enumerations should be understood by way of example and not asa limitation.

In the context of the present invention, ppm and ppb—unless statedotherwise—are understood to mean parts by weight.

The rearrangement structures mentioned occur in different amounts andratios relative to one another. The amounts thereof can be determined bytotal hydrolysis of the polycarbonate composition.

In order to determine the amount of the rearrangement structures, theparticular polycarbonate is subjected to a total hydrolysis and thecorresponding degradation products of the formulae (Ia) to (IVa) arethus formed, the amount of which is determined by HPLC. (This can bedone, for example, as follows: the polycarbonate sample is hydrolyzedunder reflux by means of sodium methoxide. The corresponding solution isacidified and concentrated to dryness. The drying residue is dissolvedin acetonitrile and the phenolic compounds of the formula (Ia) to (IVa)are determined by means of HPLC with UV detection.

Preferably, the amount of the compound of the formula (Ia) released is20 to 800 ppm, more preferably 25 to 700 ppm, and especially preferably30 to 500 ppm, based on the polycarbonate.

Preferably, the amount of the compound of the formula (IIa) released is0 (i.e. below the detection limit of 10 ppm) to 100 ppm, more preferably0 to 80 ppm and especially preferably 0 to 50 ppm, based on thepolycarbonate.

Preferably, the amount of the compound of the formula (IIIa) released is10 to 800 ppm, further preferably 10 to 700 ppm, more preferably 20 to600 ppm, and most preferably 30 to 350 ppm, based on the polycarbonate.

Preferably, the amount of the compound of the formula (IVa) released is0 (i.e. below the detection limit of 10 ppm) to 300 ppm, preferably 10to 250 ppm and most preferably 20 to 200 ppm, based on thepolycarbonate.

For reasons of simplification, the amount of the structures of theformula (I) to (IV) is equated to the respective amount of the compoundsof the formula (Ia) to (IVa) released.

The polysiloxane-polycarbonate block cocondensates obtained inaccordance with the invention likewise contain the rearrangementstructures (I) to (IV).

Based on the polysiloxane-polycarbonate block cocondensate, the amountof the compound of the formula (Ia) released after alkaline hydrolysisis preferably 20 to 800 ppm, more preferably 25 to 700 ppm, andespecially preferably 30 to 500 ppm. Preferably, the amount of thecompound of the formula (IIa) released after alkaline hydrolysis is 0(i.e. below the detection limit of 10 ppm) to 100 ppm, more preferably 0to 80 ppm and especially preferably 0 to 50 ppm, based on thepolysiloxane-polycarbonate block cocondensate. Preferably, the amount ofthe compound of the formula (IIIa) released after alkaline hydrolysis is20 to 800 ppm, further preferably 10 to 700 ppm, more preferably 20 to600 ppm, and most preferably 30 to 350 ppm, based on thepolysiloxane-polycarbonate block cocondensate. Preferably, the amount ofthe compound of the formula (IVa) released after alkaline hydrolysis is0 (i.e. below the detection limit of 10 ppm) to 300 ppm, preferably 10to 250 ppm and most preferably 20 to 200 ppm, based on thepolysiloxane-polycarbonate block cocondensate.

In a particular embodiment, polycarbonates having a water content of0.01 to 0.40 and preferably 0.05 to 0.35% by weight are used in theprocess according to the invention.

The weight-average molecular weight of the siloxane component ispreferably 3000 to 20 000 g/mol, determined by means of gel permeationchromatography and BPA (bisphenol A) Standard, and especially preferably3500-15000 g/mol.

Very particular preference is given to using, as the siloxane component,hydroxyaryl-terminated siloxanes of the formula (1) where the R² and R³radicals are both methyl and the R¹ radical is hydrogen, and p is 0.

The siloxanes of the formula (1) can be prepared by a process includingthe step of reacting a linear α,ω-bisacyloxy-polydialkylsiloxane of thegeneral formula (4) with at least one aromatic compound having at leasttwo phenolic hydroxy groups, wherein the general formula (4) is

-   -   in which    -   R⁰ is aryl, C₁ to C₁₀-alkyl or C₁ to C₁₀-alkylaryl,    -   R² and R³ are the same or different and each independently from        one another selected from aryl, C₁ to C₁₀-alkyl and C₁ to        C₁₀-alkylaryl, preferably R² and R³ are both methyl, and    -   n is a number from 1 to 500, preferably from 10 to 400,        especially preferably from 10 to 100, most preferably from 20 to        60,        and wherein the compound of formula (4) and the aromatic        compound are reacted in such a molar ratio that the ratio of the        phenolic hydroxyl groups in the aromatic compound to the acyloxy        groups in the compound of formula (4) is less than 2.0.

In a particularly preferred embodiment, the aromatic compound having atleast two phenolic hydroxy groups is a bisphenolic compound or ahydroxyl-functional oligomer thereof.

The preparation of the siloxane of formula (1) is preferably performedin an inert solvent, preferably selected from aromatic hydrocarbons suchas toluene, xylenes, chlorobenzene and the like, and polar organicacids, such as acetic acid and other C3 to C6 organic carboxylic acids.The reaction can be performed in the presence of a catalyst, which ispreferably selected from the metal salts of organic acids, such assodium or potassium acetate. Other catalysts known in the art tocatalyzed siloxane condensation reactions can also be used.

In the process according to the invention, the siloxane component of theformula (1) is used preferably in an amount of 0.5 to 50% by weight,more preferably of 1 to 40% by weight, especially preferably of 2 to20%, most preferably of 2.5 to 10% by weight and in particular 2.5% byweight to 7.5% by weight, based in each case on the polycarbonate used.

Preference is given to reacting the polycarbonate and the siloxane bymeans of catalysts. It is also possible in principle to conduct thereaction without catalyst, but in that case it may be necessary toaccept higher temperatures and longer residence times.

Catalysts suitable for the process according to the invention are, forexample, tetra alkyl ammonium catalysts, for example tetramethylammoniumhydroxide, tetramethylammonium acetate, tetramethylammonium fluoride,tetramethylammonium tetraphenylboranate, dimethyl-diphenylammoniumhydroxide, tetraethylammonium hydroxide, cetyltrimethylammoniumtetraphenylboranate and cetyltrimethylammonium phenoxide.

Especially suitable catalysts are phosphonium catalysts of the formula(5):

where R^(a), R^(b), R^(c) and R^(d) may be identical or differentC₁-C₁₀-alkyls, C₆-C₁₄-aryls, C₇-C₁₅-arylalkyls or C₅-C₆-cycloalkyls,preferably methyl or C₆-C₁₄-aryls, more preferably methyl or phenyl, andY⁻ may be an anion such as hydroxide, sulphate, hydrogensulphate,hydrogencarbonate, carbonate or a halide, preferably chloride, or analkoxide or aroxide of the formula —OR^(e) where R^(e) may be aC₆-C₁₄-aryl, C₇-C₁₅-arylalkyl or C₅-C₆-cycloalkyl, preferably phenyl.

Particularly preferred catalysts are tetraphenylphosphonium chloride,tetraphenylphosphonium hydroxide and tetraphenylphosphonium phenoxide;very particular preference is given to tetraphenylphosphonium phenoxide.

The catalyst is used preferably in amounts of 0.0001 to 1.0% by weight,preferably from 0.001 to 0.5% by weight, especially preferably from0.005 to 0.3% by weight and most preferably from 0.01 to 0.15% byweight, based on the overall composition.

The catalyst can be used alone or as a catalyst mixture and be added insubstance or as a solution, for example in water or in phenol (forexample as a cocrystal with phenol).

Catalysts suitable for the process according to the invention are thosementioned above, which are introduced into the reaction either by meansof a masterbatch with a suitable polycarbonate, especially theabove-described inventive polycarbonate, or can be added separatelytherefrom or in addition thereto.

The catalysts can be used alone or in a mixture and be added insubstance or as a solution, for example in water or in phenol.

In a preferred embodiment, reaction of the siloxane of the formula (1)and the polycarbonate is performed in presence of at least one organicor inorganic salt of an acid having a pK_(A) value within the range offrom 3 to 7 (25° C.). Suitable acids include carboxylic acids,preferably C₂-C₂₂ carboxylic acids, such as acetic acid, propionic acid,oleic acid, stearic acid, lauric acid, benzoic acid, 4-methoxybenzoicacid, 3-methylbenzoic acid, 4-tert-butylbenzoic acid, p-tolylaceticacid, 4-hydroxybenzoic acid and salicylic acid, partial esters ofpolycarboxylic acids, such as monoesters of succinic acid, partialesters of phosphoric acid, such as mono- or diorgano phosphoric acidesters, branched aliphatic carboxylic acids, such as2,2-dimethylpropanoic acid, 2,2-dimethylbutanoic acid,2,2-dimethylpentanoic acid and 2-ethylhexanoic acid.

The organic or inorganic salt is preferably used in addition to thecatalyst of formula (5); and in this embodiment the organic or inorganicsalt acts as co-catalyst.

Preferably, the organic or inorganic salt is selected from the groupconsisting of alkali metal salts, earth alkaline metal salts, quaternaryammonium salts and quaternary phosphonium salts. Useful quaternaryammonium salts are selected from tetra-(n-butyl)-ammonium,tetraphenylammonium, tetrabenzylammonium and cetyltrimethylammoniumsalts. Useful quaternary phosphonium salts are selected fronttetra-(n-butyl)-phosphonium, tetraphenylphosphonium,tetrabenzylphosphonium and cetyltrimethylphosphonium salts. Especiallypreferred are alkali metal salts and earth alkaline metal salts.

Useful organic and inorganic salts are or are derived from sodiumhydrogencarbonate, potassium hydrogencarbonate, lithiumhydrogencarbonate, sodium carbonate, potassium carbonate, lithiumcarbonate, sodium acetate, potassium acetate, lithium acetate, sodiumstearate, potassium stearate, lithium stearate, sodium oleate, lithiumoleate, potassium oleate, sodium benzoate, potassium benzoate, lithiumbenzoate, disodium, dipotassium and dilithium salts of bisphenol A.Furthermore the salts may include calcium hydrogencarbonate, bariumhydrogencarbonate, magnesium hydrogencarbonate, strontiumhydrogencarbonate, calcium carbonate, barium carbonate, magnesiumcarbonate, strontium carbonate, calcium acetate, barium acetate,magnesium acetate, strontium acetate, calcium stearate, barium stearate,magnesium stearate, strontium stearate and the respective oleates. Thesesalts may be used singly or in combination.

In a particular preferred embodiment, the salt is selected from thegroup consisting of alkali metal salts and phosphonium salts ofcarboxylic acids.

In a preferred embodiment, the salt is derived from a carboxylic acid.

The organic or inorganic salts are used preferably in amounts of 0.5 to1000 ppm, more preferably 1 to 100 ppm, and most preferably 1 to 10 ppm,based on the total weight of the siloxane and the organic or inorganicsalt. Preferably, the organic or inorganic salts are used in amounts of0.0005 to 5 mmol/kg, more preferably 0.001 to 1 mmol/kg, and mostpreferably 0.001 to 0.5 mmol/kg, based on the total weight of thesiloxane, the polycarbonate and the organic or inorganic salt.

In a preferred embodiment, the organic or inorganic salt is a sodiumsalt, preferably a sodium salt of a carboxylic acid and is preferablyused in such an amount that the sodium content in the siloxane is withinthe range of from 0.5 ppm to 100 ppm, preferably 0.8 to 50 ppm, morepreferably 1.0 to 10 ppm and in particular 1.3 to 5 ppm, based on thetotal weight of the polysiloxane-polycarbonate block cocondensate to beformed. The sodium content of the cocondensate can be determined, forexample, by atomic absorption spectroscopy with flame atomization.

Preferably, the sodium salt is used in such an amount that the sodiumcontent in the resulting polysiloxatie-polycarbonate block cocondensateis at least 50 ppb, preferably at least 80 ppb, more preferably at least100 ppb, and in particular at least 150 ppb, based on the total weightof the polysiloxane-polycarbonate block cocondensate to be formed.

In a preferred embodiment, the organic or inorganic salt is a sodiumsalt, preferably a sodium salt of a carboxylic acid and is preferablyused in such an amount that the sodium content in the resultingpolysiloxane-polycarbonate block cocondensate is within the range offrom 0.1 ppm to 1000 ppm, preferably 0.2 to 100 ppm, more preferably 0.3to 10 ppm and in particular 0.4 to 5 ppm, based on the total weight ofthe polysiloxane-polycarbonate block cocondensate to be formed. Thesodium content of the cocondensate can be determined, for example, byatomic absorption spectroscopy with flame atomization.

The organic or inorganic salt can be used alone or as a mixture and beadded in substance or as a solution. In a preferred embodiment, theinorganic or organic salt is added in form of a mixture containing thesiloxane and the organic or inorganic salt. Preferably, the mixture isobtained by mixing the siloxane and the organic or inorganic salt andoptionally one or more polar organic compounds having up to 30,preferably up to 20 carbon atoms, and at least one heteroatom,preferably selected from O, N and S, and optionally heating the mixture,for example to a temperature of 50° C. to 300° C., until it becomesclear and then cooling to room temperature. The polar organic compoundcan be removed before adding the mixture to the polycarbonate orthereafter, preferably by distillation.

Suitable polar organic compounds are selected from the group consistingof organic ketones, esters and alcohols. Alcohols, especially primaryalcohols having up to 20 carbon atoms, such as 1-octanol, 1-decanol,2-ethylhexanol, 1-dodecanol, 1,2-octanediol, benzyl alcohol,ethylhexylglycerin and oleoyl alcohol are particularly preferred.Preferably, the polar organic compound has a boiling point of less than300° C. (at 1.013 bar). The process for preparing the blockcopolycarbonates can be performed continuously or batchwise, for examplein stirred tanks, thin-film evaporators, stirred tank cascades,extruders, kneaders and simple disc reactors. The feedstocks may beblended together and melted from the start. In addition, the feedstocksmay also be added separately from one another. For instance, thepolycarbonate for use in accordance with the invention can first bemelted and the siloxane component for use in accordance with theinvention can be added at a later time. This can be done, for example,by means of liquid metering with an appropriate pump or via granulessprinkled on to polycarbonate. The catalyst can be added at any time,preferably at the start of the reaction or after the melting, in freeform or in the form of a masterbatch. The melting can be affected underair, but preferably under a protective gas atmosphere such as nitrogenor argon, or likewise preferably under reduced pressure.

The reaction is affected under the above-specified temperatures andpressures. Preference is given to shearing the reaction mixture. Thiscan be done by rapid stirring in a tank or by means of appropriatemixing elements such as static mixers, mixing elements on an extruderscrew etc. Higher mixing is preferable over low mixing. The reaction isconducted in such a way that low molecular weight constituents such aswater, phenol, linear and cyclic low molecular weight siloxane, diphenylcarbonate, bisphenol A and bisphenol A oligomers (oligocarbonates) areremoved effectively.

The reactants are preferably melted under reduced pressure. According tothe plant construction, during the melting phase, atmospheric pressure,preferably gentle vacuum, i.e. absolute pressures of lower than 200mbar, especially preferably 100-200 mbar and most preferably less than100 mbar can be applied. However, the reactants can also be melted understandard pressure, preferably under protective gas atmosphere, forexample nitrogen. The melting is preferably affected at a temperature inthe range from 250 to 400° C., more preferably in the range from 280 to380° C., most preferably in the range from 300 to 360° C. For thereaction or condensation phase, the temperatures and pressures mentionedabove apply.

Granules are obtained, if possible, by direct spinning of the melt andsubsequent granulation, or else through use of discharge extruders orgear pumps, by which spinning is affected in air or under liquid,usually water. If extruders are utilized, additives can be added to themelt upstream of this extruder, optionally with use of static mixers orby means of side extruders in the extruder.

Preferably, the polysiloxane-polycarbonate block cocondensate obtainableby the process according to the invention has a relative solutionviscosity of 1.26 to 1.40, more preferably of 1.27 to 1.38, andespecially preferably of 1.28 to 1.35, determined in dichloromethane ata concentration of 5 g/l at 25° C. using a Ubbelohde viscosimeter.Preferably, the polysiloxane-polycarbonate block cocondensate obtainableby the process according to the invention has a weight average molecularweight of 26,000 to 40,000 g/mol, more preferably 27,000 to 38,000g/mol, and most preferably 28,000 to 35,000 g/mol, determined bymeasuring the relative solution viscosity in dichloromethane at aconcentration of 5 g/l at 25° C. using a Ubbelohde viscosimeter.

It is possible to add additives and/or fillers and reinforcers to thepolysiloxane-polycarbonate block cocondensates obtainable by the processaccording to the invention. Additives are preferably used in amounts of0% by weight to 5.0% by weight, more preferably 0% by weight to 2.0% byweight, and most preferably 0% by weight to 1.0% by weight. Theadditives are standard polymer additives, for example the followingwhich are described in EP-A 0 839 623, WO-A 96/15102, EP A 0 500 496 or“Plastics Additives Handbook”, Hans Zweifel, 5th Edition 2000, HanserVerlag, Munich; flame retardants, UV stabilizers, gamma stabilizers,antistats, optical brighteners, flow improvers, thermal stabilizers,inorganic pigments, demoulding agents or processing aids. Fillers and/orreinforcers can be used in amounts of 0% by weight to 50% by weight,preferably 0% by weight to 20% by weight, more preferably 0% by weightto 12% by weight, and in particular 0% by weight to 9% by weight.

These additives, fillers and/or reinforcers can be added to the polymermelt individually or in any desired mixtures or a plurality of differentmixtures, and additives can specifically be supplied directly in thecourse of insulation of the polymer (for example via a side unit such asa side extruder) as a pure substance or as a masterbatch inpolycarbonate, or else after melting of granules in a compounding step.The additives or mixtures thereof can be added to the polymer melt insolid form, i.e. as a powder, or as a melt. Another method of meteredaddition is the use of masterbatches or mixtures of masterbatches of theadditives or additive mixtures.

In a preferred embodiment, the polymer composition comprises thermalstabilizers or processing stabilizers. Preferentially suitable arephosphites and phosphonites, and also phosphines. Examples are triphenylphosphite, diphenyl alkyl phosphite, phenyl dialkyl phosphite,tris(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite,distearyl pentaerythrityl diphosphite,tris(2,4-di-tert-butylphenyl)phosphite, diisodecyl pentaerythrityldiphosphite, bis(2,4-di-tert-butylphenyl)pentaerythrityl diphosphite,bis(2,4-di-cumylphenyl)pentaerythrityl diphosphite,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythrityl diphosphite,diisodecyloxy pentaerythrityl diphosphite,bis(2,4-di-tert-butyl-6-methylphenyl)pentaerythrityl diphosphite,bis(2,4,6-tris(tert-butylphenyl))pentaerythrityl diphosphite,tristearylsorbitol triphosphite,tetrakis(2,4-di-tert-butylphenyl)4,4′-biphenylene diphosphonite,6-isooctyloxy-2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1,3,2-dioxaphosphocin,bis(2,4-di-tert-butyl-6-methylphenyl)methyl phosphite,bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphite,6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyldibenzo[d,g]-1,3,2-dioxaphosphocin,2,2′,2″-nitrilo-[triethyltris(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite],2-ethylhexyl(3,3′,5,5′-tetra-tert-butyl-1,1′-biphenyl-2,2′-diyl)phosphite,5-butyl-5-ethyl-2-(2,4,6-tri-tert-butylphenoxy)-1,3,2-dioxaphosphirane,bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythrityl diphosphite,triphenylphosphine (TPP), trialkylphenylphosphine,bisdiphenylphosphinoethane or a trinaphthylphosphine. Especiallypreferred are triphenylphosphine (TPP), Irgafos® 168(tris(2,4-di-tert-butylphenyl)phosphite) and tris(nonylphenyl)phosphite,or mixtures thereof.

It is additionally possible to use phenolic antioxidants such asalkylated monophenols, alkylated thioalkylphenols, hydroquinones andalkylated hydroquinones. Particular preference is given to usingIrganox® 1010 (pentaerythrityl3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate; CAS: 6683-19-8) andIrganox 1076® (2,6-di-tert-butyl-4-(octadecanoxycarbonylethyl)phenol).

Suitable UV absorbers are described, for example, in EP 1 308 084 A1, inDE 102007011069 A1, and in DE 10311063 A1.

Particularly suitable ultraviolet absorbers are hydroxybenzotriazolssuch as 2-(3′,5′-bis(1,1-dimethylbenzyl)2′-hydroxyphenyl)benzotriazole(Tinuvin® 234, BASF SE, Ludwigshafen),2-(2′-hydroxy-5′-(tert-octyl)phenyl)benzotriazole (Tinuvin® 329, BASFSE, Ludwigshafen),2-(2′-hydroxy-3′-(2-butyl)5′-(tert-butyl)phenyl)benzotriazole (Tinuvin®350, BASF SE, Ludwigshafen),bis(3-(2H-benztriazolyl)2-hydroxy-5-tert-octyl)methane, (Tinuvin® 360,BASF SE, Ludwigshafen),2-(4,6-diphenyl-1,3,5-triazin-2-yl)5-(hexyloxy)phenol (Tinuvin® 1577,BASF SE, Ludwigshafen), and the benzophenones 2,4-dihydroxybenzophenone(Chimasorb® 22, BASF SE, Ludwigshafen) and2-hydroxy-4-(octyloxy)benzophenone (Chimassorb® 81, BASF SE,Ludwigshafen), 2-cyano-3,3-diphenyl-2-propenoic acid,2,2-bis[[(2-cyano-1-oxo-3,3-diphenyl-2-propenyl)oxy]methyl]1,3-propanediylester (9CI) (Uvinul® 3030, BASF AG Ludwigshafen),2-[2-hydroxy-4-(2-ethylhexyl)oxyl]phenyl-4,6-di(4-phenyl)phenyl-1,3,5-triazine(Tinuvin® 1600, BASF SE, Ludwigshafen) or tetraethyl-2,2′-(1,4-phenylenedimethylidene)bismalonate (Hostavin® B-Cap,Clariant AG). It is also possible to use mixtures of these ultravioletabsorbers.

The inventive polymer compositions may optionally comprise demouldingagents. Particularly suitable demoulding agents for the inventivecomposition are pentaerythrityl tetrastearate (PETS) or glycerylmonostearate (GMS).

In addition, it is also possible to add other polymers to the blockcocondensates obtainable in accordance with the invention, for examplepolycarbonate, polyester carbonate, polystyrene, styrene copolymers,aromatic polyesters such as polyethylene terephthalate (PET),PET-cyclohexanedimethanol copolymer (PETG), polyethylene naphthalate(PEN), polybutylene terephthalate (PBT), cyclic polyolefin, poly- orcopolyacrylates and poly- or copolymethacrylate, for example poly- orcopolymethylmethacrylates (such as PMMA), and copolymers with styrene,for example transparent polystyrene-acrylonitrile (PSAN),rubber-modified vinyl (co-)polymers, such as acrylonitrile butadienestyrene copolymer, thermoplastic polyurethanes, polymers based on cyclicolefins (e.g. TOPAS®, a commercial product from Ticona).

The block cocondensates obtainable by the process according to theinvention can be processed in a manner known for thermoplasticpolycarbonates to give any desired mouldings.

In this context, the inventive compositions can be converted, forexample, by hot pressing, spinning, blow-moulding, thermoforming,extrusion or injection moulding to products, mouldings or shapedarticles. Also of interest is the use of multilayer systems. Theapplication may coincide with or immediately follow the shaping of thebase structure, for example by coextrusion or multicomponent injectionmoulding. However, application may also be on to the ready-shaped basestructure, for example by lamination with a film or by coating with asolution.

Sheets or mouldings composed of base layer and optional toplayer/optional top layers (multilayer systems) can be produced by(co)extrusion, direct skinning, direct coating, insert moulding, filminsert moulding, or other suitable processes known to those skilled inthe art.

Injection moulding processes are known to those skilled in the art andare described, for example, in “Handbuch Spritzgiessen”, FriedrichJohannnaber/Walter Michaeli, Munich; Vienna: Hanser, 2001. ISBN3-446-15632-1 or “Anleitung zum Bau von Spritzgiesswerkzeugen”,Menges/Michaeli/Mohren, Munich; Vienna: Hanser, 1999, ISBN3-446-21258-2. Extrusion processes are known to those skilled in the artand are described, for example, for coextrusion, inter alia, in EP-A 0110 221, EP-A 0 110 238 and EP-A 0 716 919. For details of the adapterand nozzle process, see Johannaber/Ast: “Kunststoff-Maschinenführer”,Hanser Verlag, 2000 and in Gesellschaft Kunststofftechnik:“Coextrudierte Folien and Platten: Zukunftsperspektiven, Anforderungen,Anlagen and Herstellung, Qualitätssicherung”, VDI-Verlag, 1990.

The polysiloxane-polycarbonate block cocondensates obtainable by theprocess according to the invention are usable wherever the knownaromatic polycarbonates have been used to date, and wherever goodflowability coupled with improved demoulding characteristics and hightoughness at low temperatures and improved chemical resistance areadditionally required, for example for production of large externalmotor vehicle parts and switch boxes for exterior use, and of sheets,cavity sheets, electric and electronic parts, and optical memory. Forexample, the block cocondensates can be used in the IT sector forcomputer housings and multimedia housings, mobile phone cases, and inthe domestic sector, such as in washing machines, and in the sportssector, for example as a material for helmets.

EXAMPLES

The invention is described in detail hereinafter by working examples,the determination methods described here being employed for allcorresponding parameters in the present invention, in the absence of anydescriptions to the contrary.

Determination of Melt Volume Flow Rate (MVR):

The melt volume flow rate (MVR) is determined to ISO 1133 (at 300° C.;1.2 kg), unless any other conditions have been described.

Determination of Solution Viscosity (eta rel);

The relative solution viscosity (η_(rel); also referred to as eta rel)was determined in dichloromethane at a concentration of 5 g/l at 25° C.with an Ubbelohde viscometer.

Determination of Rearrangement Structures (Ia) to (IVa):

The polycarbonate sample is hydrolyzed by means of sodium methoxideunder reflux. The corresponding solution is acidified and concentratedto dryness. The drying residue is dissolved in acetonitrile and thephenolic compounds of the formulae (Ia) to (IVa) are determined by meansof HPLC with UV detection. The structures (Ia) to (IVa) areunambiguously characterized by means of nuclear magnetic resonancespectroscopy (NMR).

Determination of the Extractable Siloxane Content:

The extractable siloxane content was determined by precipitation of thecocondensate in n-hexane. For this purpose, 5 g of product weredissolved in 60 ml of dichloromethane and gradually added dropwise to750 ml of n-hexane at room temperature and while stirring. In the courseof this, the cocondensate precipitates out and settles out. Theunincorporated siloxane, in contrast, remains in solution (siloxanecomponents is soluble in n-hexane). The precipitated polymer is filteredoff and dried. A 1H NMR spectrum of the precipitated block cocondensateand of the cocondensate prior to precipitation is recorded. The decreasein the dimethylsiloxane signal at 0 ppm is evaluated compared to thesignal for the isopropylidene group at 1.67 ppm.

Materials Used:

PC 1: linear bisphenol A polycarbonate having end groups based on phenolwith a solution viscosity of 1.205 and a melt volume flow rate MVR of 59cm³/10 min (measured at 300° C. and load 1.2 kg to ISO 1033). Thispolycarbonate does not contain any additives such as UV stabilizers,demoulding agents or thermal stabilizers. The polycarbonate was preparedby means of a melt transesterification process as described in DE102008019503.

PC 2: linear bisphenol A polycarbonate having end groups based on phenolwith a melt volume flow rate (MVR) of 61.9 cm³/10 min (measured at 300°C. and load 1.2 kg to ISO 1033). The polycarbonate has a solutionviscosity of about 1.205. This polycarbonate does not contain anyadditives such as UV stabilizers, demoulding agents or thermalstabilizers. The polycarbonate was prepared via a melttransesterification process as described in DE 102008019503.

PC 3: linear bisphenol A polycarbonate having end groups based ontert-butylphenol with a solution viscosity of 1.203 and a melt volumeflow rate (MVR) of 57.2 cm³/10 min (measured at 300° C. and load 1.2 kgto ISO 1033). The polycarbonate was prepared via the interfacialprocess. Makrolon® OD2015 from Bayer MaterialScience is used.

PC 4—Oligocarbonate according to DE 19710081

Even though what is used in DE 19710081 is not a polycarbonate preparedon the industrial scale but a specifically prepared oligocarbonate, theblock cocondensate is prepared for the comparative examples based on theconditions which were described in DE 19710081.

In a three-way glass flask with stirrer and short-path separator, 150.0g (0.65 mol) of bisphenol A, 146.6 g (0.68 mol) of diphenyl carbonateare admixed with 0.027 g (0.00004 mol) of tetraphenylphosphoniumtetraphenylborate. The mixture is melted at 150° C. At a vacuum of about100 mbar and 180° C., phenol is distilled off. The vacuum is improvedstepwise down to 10 mbar over 90 minutes and the temperature isincreased to 250° C. Phenol which forms is distilled off at 250° C. and10 mbar for another 30 minutes. This gives 128 g of an oligocarbonatehaving a solution viscosity of 1.098.

Siloxane Component:

The siloxane used is hydroquinone-terminated polydimethylsiloxane of theformula (1) (i.e. R¹═H, R², R³=methyl, p=0), in which n=33.7 and m=3.7,having a hydroxy content of 11.9 mg KOH/g and a viscosity of 358 mPa's(23° C.).

The weight-average molecular weight is Mw=9100 g/mol, determined bymeans of gel permeation chromatography (GPC) with bisphenol. A standard;detection was affected by means of an IR detector at 1050 cm⁻¹.

The siloxane component can be prepared according to the followingprocedure:

In a reaction flask equipped with a thermostat heater, stirrer,thermometer, and reflux condenser, 250 g of anα,ω-bisacyloxypolydimethylsiloxane, with an average chain length of 31.8dimethylsiloxy units as determined by ²⁹Si NMR and 230 mmoles of acyloxyterminal groups, is added dropwise over 4 hours to a solution of 35.1 g(150 mmoles) bisphenol-A in 50 g xylenes, 25 g acetic acid and 0.5 g ofsodium acetate, while heating to a mild reflux at 105° C. After completeaddition the clear solution is stirred for an additional hour. Then thesolvents and volatiles are removed by vacuum distillation to 160° C.,and 3 mbar pressure. After cooling the crude product is filtered over a3 micron filter (Seitz K300) to give 236 g (83% theory) of a clear,colorless liquid.

Catalyst:

The catalyst used is tetraphenylphosphonium phenoxide from Rhein ChemieRheinau GmbH (Mannheim, Germany). The substance is used in the form of acocrystal with phenol and contains about 70% tetraphenylphosphoniumphenoxide. The amounts which follow are based on the substance obtainedfrom Rhein Chemie (as a cocrystal with phenol).

Example 1 (Comparative Example)

47.5 g of polycarbonate granules (PC 1), 2.5 g of siloxane (5% byweight) and 0.071 g of tetraphenylphosphonium phenoxide cocrystal (0.1%by weight) are weighed into a 250 ml glass flask with stirrer andshort-path separator. The apparatus is evacuated and vented withnitrogen (3× each). The mixture is melted by means of a metal bathpreheated at 350° C. under standard pressure (under nitrogen) within 10minutes. A reduced pressure is then applied. The pressure in theapparatus is about 100 mbar. The reaction mixture is kept at thisreduced pressure while stirring for 30 minutes. This is followed byventing with nitrogen and removal of the polymer melt. This gives anopaque white powder. The solution viscosity is reported in Table 1.

Example 2 (Comparative Example)

Example 2 is conducted like Example 1, except that the pressure in theapparatus in the condensation phase is 80 mbar.

Example 3 (Comparative Example)

The cocondensate is prepared as described in Example 1. In a departurefrom Example 1, PC 3 is used as the reactant. The pressure during thecondensation phase is 1.5 mbar.

Example 4 (Comparative Example)

The cocondensate is prepared as described in Example 1. In a departurefrom Example 1, PC 4 is used as the reactant. The pressure during thecondensation phase is 1.5 mbar.

Example 5 (Inventive)

The cocondensate is prepared as described in Example 1. In a departurefrom Example 1, the pressure during the condensation phase is 1.5 mbar.

Example 6 (Inventive)

The cocondensate is prepared as described in Example 1. In a departurefrom Example 1, PC 2 is used as the reactant. The pressure during thecondensation phase is 1.5 mbar.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 comparative comparativecomparative comparative inventive inventive Polycarbonate PC 1 PC 1 PC 3PC 4 PC 1 PC 2 used (reactant) Rearrangement (Ia) 75 (Ia) 75 (Ia) <10(Ia) 37 (Ia) 75 (Ia) 39 structure (IIa) <10 (IIa) <10 (IIa) <10 (IIa)<10 (IIa) (IIa) concentration (IIIa) 75 (IIIa) 75 (IIIa) <10 (IIIa) <10<10 <10 in the (IVa) 34 (IVa) 34 (IVa) <10 (IVa) <10 (IIIa) 75 (IIIa) 51polycarbonate (IVa) 34 (IVa) 28 (reactant) in ppm Phenolic OH >300 >300<300 >300 >300 >300 content in polycarbonate (reactant) in ppm Reaction350° C. 350° C. 350° C. 350° C. 350° C. 350° C. temperature Reaction 100mbar 80 mbar 1.5 mbar 1.5 mbar 1.5 mbar 1.5 mbar pressure Solution 1.1711.170 1.240 1.280 1.325 1.287 viscosity of product Colour ofwhite/light- white/light- white/light- yellow/dark- white/ white/product coloured coloured coloured coloured light- light- colouredcoloured Extractable not >40% not not <15% <15% siloxane determinable*determinable* determinable* content determined by means of NMR *InComparative Examples 1, 3 and 4, the determination of the extractablesiloxane content was not possible, since the sample was inhomogeneous.Since only a low proportion of incorporated siloxane is present, thesample separates and homogeneous sampling is impossible.

Comparative Examples 1 and 2 show that, given process parametersnormally sufficient for condensation, no increase in molecular weighttakes place. Accordingly, no reaction to give a block cocondensate takesplace. The conditions described in DE 19710081 are consequentlyinadequate to prepare a cocondensate proceeding from conventionalpolycarbonates based on bisphenol A. Even though the polycarbonate rawmaterial contains rearrangement structures, there is no reaction orincrease in molecular weight under the conditions selected.

Comparative Example 3 shows that polycarbonates which do not contain anyrearrangement structures show only an insignificant change in themolecular weight. Even though the inventive process parameters have beenmaintained, there is obviously no reaction to give high molecular weightblock cocondensates.

Comparative Example 4 was conducted with an oligocarbonate obtainedaccording to DE 19710081. The resulting molecular weight is somewhatlower compared to the inventive examples. In DE 19710081, it is alsopossible to prepare high molecular weight cocondensates, but thereaction times are distinctly different from the reaction timesdescribed here. Moreover, the condensates prepared using oligocarbonatesshow a very poor colour (see Example 4). The oligocarbonates accordingto DE19710081 do not have the inventive concentrations of therearrangement structures (Ia) to (IVa).

In contrast, Inventive Examples 5 and 6 show that, in the case of use ofthe inventive raw materials and of the process according to theinvention, high molecular weight siloxane-containing block cocondensatessimultaneously having a good colour are obtainable.

The small amounts of extractable siloxane contents in Inventive Examples5 and 6 demonstrate that polycondensation has taken place withincorporation of the siloxane component. In contrast, the comparativeexamples have a higher content of free siloxane component or aninhomogeneous sample structure.

It was extremely surprising that the process according to the inventiondescribed here can be used to prepare high molecular weight blockcocondensates in good colour quality within short reaction times. Theonly small amounts of siloxane extractable show that a high molecularweight block cocondensate has formed.

In the following examples, it was examined whether the inventive processcould be further improved by the addition of a co-catalyst.

Example 7 (Inventive)

47.5 g of polycarbonate granules (PC 1), 2.5 g of siloxane (5% byweight; without co-catalyst; sodium content of the siloxane about 0.1ppm) and 0.071 g of tetraphenylphosphonium phenoxide cocrystal (0.1% byweight) are weighed into a 250 ml glass flask with stirrer andshort-path separator. The apparatus is evacuated and vented withnitrogen (3× each). The mixture is melted by means of a metal bathpreheated at 350° C. under reduced pressure (1.5 mbar) within 10minutes. The reaction mixture is kept at this reduced pressure whilestirring for 30 minutes. This is followed by venting with nitrogen andremoval of the polymer melt. This gives an opaque white powder. Thesolution viscosity is reported in table 2.

Example 8 (Inventive)

The cocondensate is prepared as described in Example 7. In a departurefrom Example 7, the condensation phase under stirring is only 10 minutes(instead of 30 minutes). The pressure during the condensation phase is1.5 mbar. This gives an opaque white powder. The solution viscosity isreported in table 2.

Example 9 (Inventive)

The cocondensate is prepared as described in Example 7. In deviationfrom example 7 the siloxane contains sodium acetate as a co-catalyst.The sodium content in the siloxane is 1.3 ppm. The solution viscosity isreported in table 2.

Example 10 (Inventive)

The cocondensate is prepared as described in Example 9. In a departurefrom Example 9, the condensation phase under stirring is only 10 minutes(instead of 30 minutes). The pressure during the condensation phase is1.5 mbar. This gives an opaque white powder. The solution viscosity isreported in table 2.

TABLE 2 Example 7 Example 8 Example 9 Example 10 Used polycarbonate PC 1PC 1 PC 1 PC 1 Added salt — — Sodium Sodium acetate acetate Na-contentin the 0.1 ppm¹⁾ 0.1 ppm¹⁾ 1.3 ppm 1.3 ppm siloxane Time of condensation30 min 10 min 30 min 10 mm phase Solution viscosity of 1.305 1.228 1.3151.261 product ¹⁾The Na-content results from the preparation process ofthe siloxane.

As can be seen from table 2, the solution viscosity of the copolymerafter 30 minutes of condensation is similar. However, the solutionviscosity after 10 minutes is significantly higher for the materialcontaining sodium acetate. It was surprising that sodium acetate couldspeed up the molecular weight increase in the beginning of thecondensation phase while having a limited effect after prolongedcondensation time.

The invention claimed is:
 1. A process for preparingpolysiloxane-polycarbonate block cocondensates, comprising reacting atleast one hydroxyaryl-terminated siloxane of the formula (1)

in which R¹ is H, Cl, Br or C₁ to C₄-alkyl, R² and R³ are the same ordifferent and each independently from one another selected from aryl, C₁to C₁₀-alkyl and C₁ to C₁₀-alkylaryl, X is a single bond, —CO—, —O—, C₁to C₆-alkylene, C₂ to C₅-alkylidene, C₅ to C₁₂-cycloalkylidene or C₆ toC₁₂-arylene which may optionally be fused to further aromatic ringscontaining heteroatoms, n is a number from 10 to 100, m is a number from2 to 5, and p is 0 or 1; with at least one polycarbonate in the melt attemperatures of 280° C. to 400° C. and pressures of 0.001 mbar to 50mbar; wherein the polycarbonate has at least one of the followingstructures (I) to (IV):

wherein the phenyl rings are unsubstituted or independently mono- ordisubstituted by C₁ to C₈-alkyl and/or halogen, X is a single bond, C₁to C₆-alkylene, C₂ to C₅-alkylidene or C₅ to C₆-cycloalkylidene, and thelinkages indicated by --- in the structural units (I) to (IV) are eachpart of a carboxylate group; wherein the amount of the structural units(I) to (IV) totals 50 to 2000 ppm (determined after hydrolysis, based onthe polycarbonate), and wherein the polycarbonate has a weight-averagemolecular weight of 16 000 to 28 000 g/mol.
 2. The process according toclaim 1, wherein the amount of the structural units (I) to (IV) totals80 to 850 ppm (based on the polycarbonate and determined afterhydrolysis).
 3. The process according to claim 1, wherein thepolycarbonate has phenolic OH groups in an amount of 250 ppm to 1000ppm.
 4. The process according to claim 1, wherein thehydroxyaryl-terminated siloxane has a weight-average molecular weight of3000-20 000 g/mol.
 5. The process according to claim 1, wherein thehydroxyaryl-terminated siloxane is used in an amount of 2 to 20% byweight, based on the polycarbonate used.
 6. The process according toclaim 1, wherein R¹ is H, p is 1 and X is isopropylidene.
 7. The processaccording to claim 1, wherein R² and R³ are methyl.
 8. The processaccording to claim 1, wherein a phosphonium catalyst of the formula ofthe formula (5) is used during the reaction:

where R^(a), R^(b), R^(c) and R^(d) may be identical or differentC₁-C₁₀-alkyls, C₆-C₁₄-aryls, C₇-C₁₅-arylalkyls or C₅-C₆-cycloalkyls, andY— may be an anion selected from the group consisting of hydroxide,sulphate, hydrogensulphate, hydrogencarbonate, carbonate, halide or analkoxide or aroxide of the formula —OR^(e) where R^(e) is C₆-C₁₄-aryl,C₇-C₁₅-arylalkyl or C₅-C₆-cycloalkyl.
 9. The process according to claim1, wherein the siloxane and the polycarbonate are reacted in thepresence of at least one organic or inorganic salt of an acid having apK_(A) value within the range of from 3 to 7 (25° C.).
 10. The processaccording to claim 9, wherein the organic or inorganic salt is selectedfrom the group consisting of alkali metal salts, earth alkaline metalsalts, quaternary ammonium salts and quaternary phosphonium salts. 11.The process according to claim 9, wherein the one or more organic orinorganic salts are used in amounts of 0.5 to 1000 ppm, based on thetotal weight of the siloxane and the organic and/or inorganic salt(s).12. The process according to claim 1, wherein the process is performedat pressures of 0.02 to 30 mbar.